1. Field of the Invention
The present invention relates generally to a viscous fluid type heat generator in which a viscous fluid is subjected to a shearing action to generate heat that is in turn transmitted to a circulating heat-transfer or heat-exchange fluid in a heat receiving chamber, and is carried by the heat-transfer fluid to a desired heated area, such as a passenger compartment in an automobile. More particularly, the present invention relates to a viscous fluid type heat generator adapted for being used as a supplementary heat source incorporated in an automobile heating system and having such a construction thereof able to regulate heat generation in response to either a change in an environment in which the viscous fluid type heat generator is used or a change in an operating condition of the heat generator, i.e., an operating speed of the viscous fluid type heat generator.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 2-246823 (JP-A-2-246823) discloses a typical automobile heating system in which a viscous fluid type heat generator, to generate heat by using a viscous fluid generating heat when it is subjected to shearing action, is incorporated. The viscous fluid type heat generator disclosed in JP-A-2-246823 includes a pair of mutually opposing front and rear housings tightly secured together by appropriate tightening elements, such as through bolts to define an inner heat generating chamber and a heat receiving chamber arranged adjacently to the heat generating chamber but separated by a partition wall through which the heat is exchanged between the viscous fluid in the heat generating chamber and the water in the heat receiving chamber. The heat exchanging water is introduced into the heat receiving chamber through a water inlet port and delivered from the heat receiving chamber toward an external heating system, and the water is constantly circulated through the heat generator and the external heating system.
A drive shaft is rotatably supported in the front housing via anti-friction bearing so as to support thereon a rotor element in such a manner that the rotor element is rotated with the drive shaft within the heat generating chamber. The rotor element has outer faces which are face-to-face with the inner wall faces of the heat generating chamber and form labyrinth grooves therebetween, and a viscous fluid is supplied into the heat generating chamber so as to fill the labyrinth grooves between the rotor element and the wall faces of the heating chamber.
When the drive shaft of the viscous fluid type heat generator incorporated in the automobile heating system is driven by an automobile engine, the rotor element is also rotated within the heat generating chamber so as to apply a shearing action to the viscous fluid held between the wall surfaces of the heat generating chamber and the outer surfaces of the rotor element. Thus, the viscous fluid which typically consists of a polymer material, typically a silicone oil having a chain molecular structure presenting a high viscosity, generates heat due to the shearing action applied thereto. The heat is transmitted from the viscous fluid to the heat exchanging water flowing through the heat receiving chamber. The heat exchanging water carries the heat to the heating circuit of the automobile heating system.
In the above-described viscous fluid type heat generator according to the prior art, when the rotor element is rotated about an axis of rotation thereof at a given rotating speed, a radially outer portion thereof far from the axis of rotation thereof has a circumferential speed larger than that of a radially inner portion of the rotor element located around the axis of rotation of the rotor element. Therefore, the outer portion of the rotor element can provide the viscous fluid within the heat generating chamber with a shearing action to generate heat which is more effective than that provided by the inner portion of the rotor element. Namely, the radially outer portion of the rotor element can make a contribution to the heat generation by the viscous fluid greater than the radially inner portion of the rotor element. Accordingly, if the viscous fluid type heat generator is used in either an environmental condition such that the atmospheric temperature is constantly low or an operating condition such that a large part of the operation of the viscous fluid type heat generator includes a low rotating speed operation of the drive shaft and the rotor element, a viscous fluid type heat generator is required to have a capability of forcibly moving the viscous fluid within the heat generating chamber from a region adjacent to the radially inner portion of the rotor element toward a different region adjacent to the radially outer portion thereof, so that a stronger shearing action can be applied to the viscous fluid.
Further, it should be understood that if the viscous fluid held to be in contact with the inner wall surfaces of the heat generating chamber and the outer surfaces of the rotor element is able to have a larger contacting area within the heat generating chamber, the viscous fluid can generate a greater amount of heat during the rotation of the rotor element.
When the rotor element of a viscous fluid type heat generator is constantly rotated at a high speed, the viscous fluid within the heat generating chamber is constantly subjected to a strong shearing action to thereby generate an excessive amount of heat, and as a result, the viscous fluid is thermally degraded after a relatively short operating life of the heat generator. Therefore, if the viscous fluid type heat generator is used in either an environmental condition such that the temperature is constantly warm or hot or an operating condition such that a large part of operation of the heat generator includes a high rotating speed operation of the drive shaft and the rotor element, the viscous fluid type heat generator is required to have a capability of forcibly moving the viscous fluid within the heat generating chamber from a region adjacent to the radially outer portion of the rotor element toward a separate region adjacent to the radially inner portion thereof.
Nevertheless, the viscous fluid type heat generators according to the prior art, e.g., the heat generator as disclosed in JP-A-2-246823, are not provided with any means to realize the above-mentioned two capabilities.